Avenir Expander 2.0 Seat Bag (Medium- 61/110 Cubic Inches) Expandable bicycle seat bag made of 420-denier ripstop nylon Stretches from 61 to 110 cubic inches for storing extra gear Parallel zip design for easy access; wraparound reflective stripe Hook-and-loop mounting system attaches securely to seat Rear tab holds reflective taillight (sold separately)